System and method for scanned ion beam interplay effect mitigation using random repainting

ABSTRACT

Interference of dose application in scanned ion beam therapy and organ motion, also called interplay effect, may lead to dose deviations at target volumes. Current repainting methods are susceptible to artefacts due to a predominant scanning direction, ranging from fringed field edges to under and overdosed regions (hot and cold spots). To overcome the difficulties inherent in the repainting techniques of conventional proton therapy systems, new random repainting techniques are described herein for mitigating the under-dose and/or over-dose pattern inherent in existing repainting techniques using a random repainting approach that randomly selects spot locations within the target area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is related to and incorporates by referenceherein in their entirety, the following patent application that isco-owned and concurrently filed herewith:

-   (1) U.S. patent application Ser. No. 15/087,292, entitled Automatic    “ADAPTIVE PENCIL BEAM SCANNING” by Wulff et al., with filing date of    Mar. 31, 2016, Attorney Docket No. VAR-15-041-US.-   (2) U.S. patent application Ser. No. 15/087,800, entitled Automatic    “SYSTEM AND METHOD FOR IN-LAYER SYNCHRONIZATION FOR FAST SPOT    RESCANNING” by Bach et al., with filing date of Mar. 31, 2016,    Attorney Docket No. VAR-15-004-US.

TECHNICAL FIELD

Embodiments of this invention relate generally to directed irradiatedparticle beam applications. More specifically, embodiments of thisinvention are directed to improved methods and systems for directing abeam of irradiated particles to achieve a target dosage using a randomrepainting technique.

BACKGROUND OF THE INVENTION

Particle therapy is a type of external beam radiotherapy that generatesbeams of energetic protons, neutrons, or ions used for cancer treatment.Particle therapy works by providing energetic ionizing particles totarget tissue (e.g., a tumor). These particles are used to destroy ordamage the DNA of tissue cells.

Ion therapy is a type of external beam radiation therapy that ischaracterized by the use of a beam of ions to irradiate diseased tissue.A chief advantage of ion therapy over other conventional therapies suchas X-ray or neutron radiation therapies is that ion radiation has theability to stop in matter—treatment dosages are applied as a sequence ofproton beams with several energies three-dimensionally. The dosedeposition of each monoenergetic, thin (“pencil”) beam in a medium ischaracterized by a sharp increase in dose deposition (Single Bragg Peak)directly before the end of the beam depth, thereby limiting theinadvertent exposure of non-target cells to potentially harmfulradiation.

The pencil beam scanning technique allows the deflection ofmonoenergetic beams to prescribed voxels (in transversal direction/x-and y-coordinates for associated beam depths) in medium—the so calledspot scanning technique (e.g., a “raster scan” of applications).Prescribed spot positions for a scanned ion beam delivery are typicallyarranged on a fixed (raster) pattern for each energy and thereforedeliverable on a fixed scanning path within an energy layer (for exampleon a meander like path). By superposition of several ion beams ofdifferent energies, a Bragg peak can be spread out to cover targetvolumes by a uniform, prescribed dose. This enables ion therapytreatments to more precisely localize the radiation dosage relative toother types of external beam radiotherapy. During ion therapy treatment,a particle accelerator such as a cyclotron or synchrotron, is used togenerate a beam of ions from, for example, an internal ion sourcelocated in the center of the cyclotron. The ions in the beam areaccelerated (via a generated electric field), and the beam ofaccelerated ions is subsequently “extracted” and magnetically directedthrough a series of interconnecting tubes (called a beamline), oftenthrough multiple chambers, rooms, or even floors of a building, beforefinally being applied through an end section of beamline (called Nozzle)to a target volume in a treatment room.

As the volumes (e.g., organs, or regions of a body) targeted forradiation therapy are often below the surface of the skin and/or extendin three dimensions, and since ion therapy—like all radiationtherapies—can be harmful to intervening tissue located in a subjectbetween the target area and the beam emitter, the precise calculationand application of correct dosage amounts and positions are critical toavoid exposing non target areas to the radiation beyond what isnecessary. However, the effective ion range is variable based on anumber of uncertainties, such as positional discrepancies and motion,and understanding of the sources and magnitude of these uncertainties iskey for producing treatment plans which are robust and can withstandthese uncertainties. Furthermore, for intensity-modulated particletherapy (IMPT), steep dose gradients are often used at the target borderand field edges to enhance dose conformity. This increases thecomplexity of fluence maps and decreases robustness to uncertainties.

To address these issues, adaptive therapy techniques have been proposedthat incorporate such uncertainties directly into the optimizationalgorithm. According to some techniques, robustness may be included in amulti-criteria optimization framework, allowing a multi-objectiveoptimization function to balance robustness and conformity. Formitigating the effects of motion specifically, rescanning (“repainting”)techniques have been developed to deliver the prescribed dosedistribution to each layer of the target volume. However, the repaintingtechniques currently employed lead to an under-dose and/or over-dosepattern based on motion parameters (e.g., initial phase, period,amplitude) and the speed and/or direction of the scanning, leading toartefacts caused by a predominant scanning direction. What is needed isan approach to repainting that mitigates the under-dose and/or over-dosepattern inherent in existing repainting techniques while achieving arelatively uniform dose distribution.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that is further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

To overcome the difficulties inherent in the repainting techniques ofconventional proton therapy systems, such as effects caused by scanningdirection and speed, new random repainting techniques are describedherein for mitigating the under-dose and/or over-dose pattern inherentin existing repainting techniques. According to one embodiment, a methodfor irradiating a target area using randomly distributed spot locationsis disclosed. The method includes accessing a target radiation plan, thetarget radiation plan including a temporal and spatial sequence foradministering a target dosage to a target area using a plurality ofapplications of a directed beam of protons, monitoring a movement of thetarget area, adjusting the target radiation plan to align the pluralityof applications of the directed beam of protons with a movement of thetarget area to generate an adjusted target radiation plan, applying adirected beam of protons to a first set of spot locations of the targetarea according to the adjusted target radiation plan, where the firstset of spot locations are selected at random, and applying the directedbeam of protons to a second set of spot locations of the target areaaccording to the adjusted target radiation plan, where the second set ofspot locations are selected at random.

According to another embodiment, a radiation application system isdisclosed. The radiation application system includes a particleaccelerator configured to produce a plurality of irradiated particles, agantry configured to receive the plurality of irradiated particles andto rotate around a target subject, a treatment nozzle included in thegantry, the treatment nozzle configured to emit the plurality ofirradiated particles as a directed beam at a target area in the targetsubject, a sensor device configured to monitor a movement of the targetarea, and a client computing device. The client computing deviceincludes a memory device configured to store a target radiation planincluding a timed sequence for administering a target dosage to thetarget area using a plurality of applications of the directed beam ofirradiated particles, where the plurality of applications include aplurality of spot locations selected at random, and a processorconfigured adjust the target radiation plan to align the plurality ofapplications of the directed beam of protons with a movement of thetarget area, and to program a movement of the gantry around the targetsubject and an emission of the treatment nozzle to apply the directedbeam of irradiated particles at the plurality of spot locations selectedat random for the target area according to the adjusted target radiationplan.

According to another embodiment, a non-transitory computer readablemedium having a plurality of programmed instructions which, whenexecuted by a processor in a computing system, is operable to implementa target radiation plan using randomly distributed spot locations. The anon-transitory computer readable medium includes instructions to accessa target radiation plan, the target radiation plan including a timedsequence for administering a target dosage to a target area using aplurality of applications of a spot-scanning beam of protons,instructions to monitor a periodic movement of the target area,instructions to generate an adjusted target radiation plan by adjustingthe target radiation plan align the plurality of applications of thedirected beam of protons with a movement of the target area,instructions to apply a directed beam of protons to a first set of spotlocations of the target area according to the adjusted target radiationplan, where the first set of spot locations are selected at random, andinstructions to apply the directed beam of protons to a second set ofspot locations of the target area according to the adjusted targetradiation plan, where the second set of spot locations are selected atrandom.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the disclosure and,together with the description, serve to explain the principles of thepresently claimed subject matter:

FIG. 1 depicts an exemplary proton therapy device in accordance withembodiments of the present invention.

FIG. 2 depicts exemplary interplay effect for parallel scanning andperpendicular scanning of an organ in motion compared to a static case.

FIG. 3 depicts an exemplary motion cycle of a 4×random repaintingapplication according to embodiments of the present invention.

FIG. 4A illustrates an absolute dose measurement of an exemplary4×random repainting application for a target in motion according toembodiments of the present invention.

FIG. 4B illustrates an absolute dose measurement of an exemplaryconventional repainting application for a target in motion.

FIG. 5A illustrates an integrated dose distribution of a 4×randomrepaint according to embodiments of the present invention.

FIG. 5B illustrates an integrated dose distribution of a conventionalrepaint.

FIG. 6 illustrates a sequence of three paints of an exemplary randomrepaint process according to embodiments of the present invention.

FIG. 7 is a flowchart depicting an exemplary sequence of steps forperforming a random repaint application according to embodiments of thepresent invention.

FIG. 8 depicts an exemplary computing environment, in accordance withembodiments of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to several embodiments. While thesubject matter will be described in conjunction with the alternativeembodiments, it will be understood that they are not intended to limitthe claimed subject matter to these embodiments. On the contrary, theclaimed subject matter is intended to cover alternative, modifications,and equivalents, which may be included within the spirit and scope ofthe claimed subject matter as defined by the appended claims.

Furthermore, in the following detailed description, numerous specificdetails are set forth in order to provide a thorough understanding ofthe claimed subject matter. However, it will be recognized by oneskilled in the art that embodiments may be practiced without thesespecific details or with equivalents thereof. In other instances,well-known processes, procedures, components, and circuits have not beendescribed in detail as not to unnecessarily obscure aspects and featuresof the subject matter.

Portions of the detailed description that follow are presented anddiscussed in terms of a process. Although operations and sequencingthereof are disclosed in a figure herein (e.g., FIG. 7) describing theoperations of this process, such operations and sequencing areexemplary. Embodiments are well suited to performing various otheroperations or variations of the operations recited in the flowchart ofthe figure herein, and in a sequence other than that depicted anddescribed herein.

Some portions of the detailed description are presented in terms ofprocedures, operations, logic blocks, processing, and other symbolicrepresentations of operations on data bits that can be performed oncomputer memory. These descriptions and representations are the meansused by those skilled in the data processing arts to most effectivelyconvey the substance of their work to others skilled in the art. Aprocedure, computer-executed operation, logic block, process, etc., ishere, and generally, conceived to be a self-consistent sequence ofoperations or instructions leading to a desired result. The operationsare those requiring physical manipulations of physical quantities.Usually, though not necessarily, these quantities take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, compared, and otherwise manipulated in a computer system. Ithas proven convenient at times, principally for reasons of common usage,to refer to these signals as bits, values, elements, symbols,characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout, discussions utilizingterms such as “accessing,” “writing,” “including,” “storing,”“transmitting,” “traversing,” “associating,” “identifying” or the like,refer to the action and processes of a computer system, or similarelectronic computing device, that manipulates and transforms datarepresented as physical (electronic) quantities within the computersystem's registers and memories into other data similarly represented asphysical quantities within the computer system memories or registers orother such information storage, transmission or display devices.

It is appreciated that throughout, discussions utilization of the term“painting”, “repainting”, “scanning”, or “rescanning” shall refer toirradiating a target area with a proton beam.

While the following example configurations are shown as incorporatingspecific, enumerated features and elements, it is understood that suchdepiction is exemplary. Accordingly, embodiments are well suited toapplications involving different, additional, or fewer elements,features, or arrangements.

Random Repainting for Scanned Ion Beam Interplay Effect Mitigation

The claimed subject matter is directed to a particle beam controlsystem. To overcome the difficulties inherent in the repaintingtechniques of conventional proton therapy systems, new random repaintingtechniques are described herein for mitigating the under-dose and/orover-dose pattern inherent in existing repainting techniques. Accordingto one embodiment, a method for irradiating a target area using randomlydistributed spot locations is disclosed. The method includes accessing atarget radiation plan, the target radiation plan including a temporaland spatial sequence for administering a target dosage to a target areausing a plurality of applications of a directed beam of protons,monitoring a movement of the target area, adjusting the target radiationplan to align the plurality of applications of the directed beam ofprotons with a movement of the target area to generate an adjustedtarget radiation plan, applying a directed beam of protons to a firstset of spot locations of the target area according to the adjustedtarget radiation plan, where the first set of spot locations areselected at random, and applying the directed beam of protons to asecond set of spot locations of the target area according to theadjusted target radiation plan, where the second set of spot locationsare selected at random.

According to another embodiment, a radiation application system isdisclosed. The radiation application system includes a particleaccelerator configured to produce a plurality of irradiated particles, agantry configured to receive the plurality of irradiated particles andto rotate around a target subject, a treatment nozzle included in thegantry, the treatment nozzle configured to emit the plurality ofirradiated particles as a directed beam at a target area in the targetsubject, a sensor device configured to monitor a movement of the targetarea, and a client computing device. The client computing deviceincludes a memory device configured to store a target radiation planincluding a timed sequence for administering a target dosage to thetarget area using a plurality of applications of the directed beam ofirradiated particles, where the plurality of applications include aplurality of spot locations selected at random, and a processorconfigured adjust the target radiation plan to align the plurality ofapplications of the directed beam of protons with a movement of thetarget area, and to program a movement of the gantry around the targetsubject and an emission of the treatment nozzle to apply the directedbeam of irradiated particles at the plurality of spot locations selectedat random for the target area according to the adjusted target radiationplan.

According to another embodiment, a non-transitory computer readablemedium having a plurality of programmed instructions which, whenexecuted by a processor in a computing system, is operable to implementa target radiation plan using randomly distributed spot locations. The anon-transitory computer readable medium includes instructions to accessa target radiation plan, the target radiation plan including a timedsequence for administering a target dosage to a target area using aplurality of applications of a spot-scanning beam of protons,instructions to monitor a periodic movement of the target area,instructions to generate an adjusted target radiation plan by adjustingthe target radiation plan align the plurality of applications of thedirected beam of protons with a movement of the target area,instructions to apply a directed beam of protons to a first set of spotlocations of the target area according to the adjusted target radiationplan, where the first set of spot locations are selected at random, andinstructions to apply the directed beam of protons to a second set ofspot locations of the target area according to the adjusted targetradiation plan, where the second set of spot locations are selected atrandom.

Exemplary Radiation Therapy Device

FIG. 1 depicts an exemplary radiation therapy device 100 in a treatmenttherapy room, in accordance with various embodiments of the claimedsubject matter. As presented in FIG. 1, radiation therapy device 100includes a gantry 101, a radiation treatment nozzle 103, and a subjectpositioner 105. In one or more embodiments, the gantry 101 may comprisean opening through which at least a portion of the subject positioner105 is able to enter (e.g., via automatic and/or mechanical means). Inone or more embodiments, at least a portion of the gantry may beoperable to rotate around the opening (typically while at least aportion of the subject positioner is disposed within). For example, asdepicted in FIG. 1, the gantry 101 may be implemented as a ring, atleast a portion of which may be rotatable around an axis bisected by thesubject positioner 105.

According to one or more embodiments, the gantry 101 is configured toreceive irradiated particles through a beam line connected to a particleaccelerator (not shown). The particle accelerator may be implemented as,but is not limited to, a proton accelerator such as a cyclotron orsynchrotron. In one or more embodiments, the particle accelerator may bepositioned remotely with respect to the treatment therapy room and maybe shared between multiple radiation therapy devices housed in multipletreatment therapy rooms. Beam lines (e.g., vacuum sealed tubes or pipesused to transfer irradiated particles) are used to connect the particleaccelerator to each of the radiation therapy devices. The irradiatedparticles are emitted from the radiation therapy device 100 through thetreatment nozzle 103 located on the gantry 101. In one or moreembodiments, the treatment nozzle 103 is rotated about the opening ofthe gantry 101 through a rotation of at least a portion of the gantry.In alternate embodiments, movement of the treatment nozzle 103 may beperformed via movement of one or more robotic appendages coupled to thegantry 101.

In one or more embodiments, the subject positioner 105 may include asupport structure (such as a table, chair, bench, or bed) upon which atreatment subject may lie, sit, or rest upon. According to furtherembodiments, portions of the subject positioner 105 may be capable ofmovement, via automatic and/or mechanical means. For example, theincline of a portion of the resting surface may be increased ordecreased (e.g., physically via a mechanism or automatically through agraphical user interface). Portions of the subject positioner 105 mayalso be equipped with means to rotate, extend, or retract. For example,according to one or more embodiments, a portion of the resting surfaceof the subject positioner 105 may be extended or physically positionedinto an opening of the gantry 101, such that a treatment subject restingon the subject positioner 105 bisects the plane at which the treatmentnozzle 103 is directed.

One or both of the gantry 101 and the subject positioner 105 is/arecapable of maneuvering, either independently or in conjunction, to aligna treatment subject positioned on the subject positioner 105 with atreatment nozzle 103. Movement of the gantry 101 and/or subjectpositioner 105 may include, but is not limited to, rotation, extension,retraction, contraction, adduction, abduction, etc. of one or morearticulated surfaces or portions of the gantry 101, and/or subjectpositioner 105. In one or more embodiments, treatment nozzle 103 mayalso be capable of limited movement, via multi-axial rotation, forexample. Movement of the gantry 101, treatment nozzle 103, and/orsubject positioner 105 may be performed automatically, viapre-programmed instructions that correspond to optimized alignments fordesired iso-centers, or may be controlled remotely via a user interface.

A treatment subject may be positioned (e.g., by lying prone) on asubject positioner 105 at an initial or starting position. One or moreportions of the subject positioner 105 may extend towards an openingpresented by the gantry 101, such that a target region of the treatmentsubject is aligned with a position of the treatment nozzle 103, locatedon or around an inner surface of the gantry 101. In alternate or furtherembodiments, the gantry 101 may also rotate in an arc around thecircumference of the gantry 101 to position the treatment nozzle 103 toproduce the desired beam field or to do position verification of atreatment subject positioned on a subject positioner 105. Once thegantry 101, treatment nozzle 103, and/or subject positioner 105 arealigned in the desired orientation, treatment therapy may begin.Specifically, an iso-center in the treatment subject may be aligned withthe treatment nozzle 103 via movement of the gantry 101 and/or subjectpositioner 105. In one or more embodiments, treatment therapy maycomprise the application of irradiated particles generated at a (remote)particle accelerator, received in the gantry 101, and emitted (e.g., asa raster scan) in a beam field from the treatment nozzle 103 at aniso-center located in a treatment subject according to a pre-determinedtreatment therapy plan.

The treatment nozzle 103 may be configured to emit the irradiateparticles in a spot scanning beam (also referred to as a “pencil beam”).Adjusting the energy level of the beam allows control of the depth atwhich the Bragg Peaks of the accelerated protons are located. Theincreased flexibility made available through three-dimensional spotscanning greatly improves the precision of the dose delivered to apatient so as to maximize dose delivery to a tumor and minimize damageto healthy tissue.

A spot-scanning beam may be produced by crossing two or more extractedbeams at an extremely fine point in the radiation device. A target area(beam field) may be irradiated with a raster scan (two-dimensionalemission) of the resultant spot scanning beam. In one or moreembodiments, multiple beam fields sharing the same or proximateiso-centers may be irradiated with the spot scanning beam in acontiguous session, uninterrupted by application of the spot scanningbeam to more distant or unrelated beam fields, for example. In furtherembodiments, beam fields that do not require the addition and/or removalof additional accessories such as (but not limited to) collimators,jaws, and range shifters, etc., may be irradiated in a contiguous beamapplication, as an automated treatment of a set of fields.

In one or more embodiments, a subject resting or positioned on thesubject positioner may be monitored. For example, the motion of a targetarea within the subject may be monitored by, but is not limited to,continuous imaging the target volume and/or tracking one or more motionsurrogates directly correlated to the motion and/or position of a targetvolume (not shown). These surrogates may include, for example,respiratory markers or ECG signals. Other methods for monitoring atarget area may include, but are not limited to, implanted sensors,real-time imaging devices, or any other device suitable to monitor organmotion and/or the respiratory or cardiac cycle(s) of a subject.Monitoring of a target area may include measuring a frequency andduration of each phase or cycle of a periodic motion exhibited by thetarget area (e.g., displacement from a resting or default position) andthe timing (e.g., duration) of transitions between phases. Monitoring ofa target area may also include measuring the direction and the peakdisplacement from the resting or default position, mapped to phases ofthe periodic motion.

The monitored motion may be analyzed and the analyzed motioncharacteristics may be used, but are not limited, to adjust the timing,direction and sequence of directed particle beam radiation associatedwith prescribed radiation plans to better align beam applications toaccount for the motion exhibited by the target area. In one or moreembodiments, the radiation plan may be stored with other radiation plansas a plurality of programmed instructions in a memory device of acontroller (e.g., a computing device executing an application) of theradiation therapy device 100 and the emission of the beam of irradiatedparticles.

Random Repainting Results

A simulation tool based on treatment logs and motion information wasdeveloped to compare measurement results to expected dose distributions.Efficiency of repainting was analyzed by comparison to the static case.Quantitative analysis was performed with PTW VeriSoft 6.2. Simulationsusing mono-energetic plans with a 10×10 cm² scanning field sizecalculated by the Eclipse 13 treatment planning system demonstrateexemplary random repainting realized by randomly distributing singlespot locations. Measurements were performed using an IAS, atwo-dimensional amorphous silicon detector (relative dose measurementsin air at isocenter) and a PTW 729XDR (absolute dose measurements withslabs of phantom material in front of the detector), both mounted to amotion platform (CIRS dynamic platform). Motion was considered withdifferent cycles, directions and translations up to ±8 mm. Measurementswere performed for a static case as reference, conventional repainting(repeated meander-like path), and random repainting.

Interference of dose application in scanned ion beam therapy and organmotion, also called interplay effect, may lead to dose deviations attarget volumes. Current repainting methods are susceptible to artefactsdue to a predominant scanning direction, ranging from fringed fieldedges to under and overdosed regions (hot and cold spots). With regardto FIG. 2, interplay effect for parallel scanning 202 and perpendicularscanning 203 with organ motions of 4 mm and 3.7 s are compared to astatic case 201. For moving objects, the predominant scanning directionof the ion beam (e.g., proton beam) may interfere with the inner bodymotion of the target (interplay effect), resulting in a distorted dosedistribution. Additional target margins will not mitigate the interplayeffect if scanning and organ motions are perpendicular to each othercausing to hot and cold regions to develop.

With regard to FIG. 3, an exemplary motion cycle of a 4×randomrepainting application 301 is depicted according to embodiments of thepresent invention. A setup with parallel and orthogonal motion waschosen to contribute both types of artefacts. Summing up individual spotdoses during a single random repaint demonstrates the mitigation ofdescribed interplay effects, where repainting techniques are used toblur or smear the interplay effects. Embodiments of the presentinvention repaint more effectively by randomizing the repainting spotpattern as depicted in FIG. 3 such that the irradiation has nopredominant direction. These techniques yield considerable improvementsin dose conformity for randomly repainting a single layer, therebysuperseding motion path considerations for target and scanning order toprevent hot and cold spots during treatment planning. When applied tomultiple layers, these techniques may reduce target margins and thenumber of repaints (rescans) necessary to achieve a target dose comparedto conventional approaches. High resolution measurements of four randomrepaints with oblique target motion of ±4 mm reveals a moderatedeviation from the reference case 201. The increased overall scanningtravel distance leads to a prolonged irradiation time (e.g., 20.2 s orhigher) compared to 17.4 s for the conventional approach with the samenumber of repaints and 10.7 s without repainting.

With regard to FIGS. 4A and 4B, exemplary absolute dose measurements 401and 402 demonstrate that a higher pass rate for Gamma 3%/3 mm can beachieved (93.7% vs. 68.5%) with random repainting, making it moretime-efficient for achieving the same plan quality. In other words, therandom repainting technique uses less paint (application of irradiation)compared to the conventional approach. FIG. 4A illustrates an absolutedose measurement 401 of an exemplary 4×random repainting applicationwith target motion ±4 mm and 3.7 s according to embodiments of thepresent invention. FIG. 4B illustrates an absolute dose measurement 402of a conventional repainting technique for target oblique shifts by ±4mm and a 3.7 s motion cycle (without random repainting).

With regard to FIG. 5A and 5B, exemplary integrated dose distributionsfor 4×random repainting applications with oblique shifts of ±8 mm and7.2 s motion cycle are depicted according to embodiments of the presentinvention. FIG. 5A illustrates an integrated dose distribution 501 of a4×random repaint with a potential motion amplitude pass rates of 82.8%.FIG. 5B illustrates an integrated dose distribution 502 of aconventional repaint (without random repainting).

With regard to FIG. 6, three paints (scans) 601-603 of an exemplaryrandom repaint process 600 are depicted according to embodiments of thepresent invention. Subsequent to paint 601, areas with not enough dose604 (cold spots) and areas with too much dose 605 (hot spots) arepresent in the target region. Subsequent to paint 602, the hot and coldspots have been blended together. The random paint process 600 endssubsequent to paint 603, and a uniform target dose distribution isachieved.

With regard to FIG. 7, a flow chart depicting an exemplary sequence ofsteps for irradiating a target area with a proton beam using randomrepainting to achieve a uniform dose distribution and mitigate interplayeffects is depicted according to embodiments of the present invention.Steps 701-707 describe exemplary steps comprising the process 700depicted in FIG. 7 in accordance with the various embodiments hereindescribed. In one embodiment, the process 700 is implemented in whole orin part as computer-executable instructions stored in acomputer-readable medium and executed in a computing device.

At step 701, a radiation plan is received or accessed for a target areaof a radiation subject. In one or more embodiments, the radiation planmay comprise a proton therapy plan for a patient undergoing radiation(proton-therapy) treatment. According to one or more embodiments, theradiation plan is received as data in a computing device executing anapplication operable to control a proton therapy treatment machine. Theradiation plan may be pre-generated and associated with the radiationsubject, and stored as one of a multitude of pre-generated recordsassociated with a corresponding multitude of radiation subjects.According to some embodiments, the radiation plan includes a randompattern of locations used for random repainting. In still furtherembodiments, the radiation plan may be include a timing sequence andposition data for applications of a random spot-scanning proton beamduring a treatment session.

At step 703, a motion of the target area is monitored. Motion of thetarget area may be monitored by, but is not limited to, continuousimaging the target volume and/or tracking one or more motion surrogatesdirectly correlated to the motion and/or position of a target volume. Inone or more embodiments, the motion may be monitored indirectly bymonitoring a displacement of an adjacent field or object. Motion data istracked using the sensors, and characteristics of periodic motions(e.g., inhalation and exhalation, heartbeats) exhibited by the targetarea are measured. These characteristics may include, for example, afrequency of a periodic motion, the duration of each phase in theperiodic motion, and the timing of any transition period between eachphase.

At step 705, the radiation plan received in step 701 is dynamicallyadjusted to align the timing sequences and position data of the scanningapplication with the periodic motion exhibited by the target areameasured in step 703. Adjusting the radiation plan may be accomplishedby a variety of beam and periodic motion characteristics. For example, astarting position of an application of a spot-scanning beam can bealigned with a phase of periodic movement such as a respiratory motionby altering the start position of each scan to begin at an arbitraryposition within the target area during each phase in the periodicmotion. Other characteristics of the beam may be aligned with the motionof the target area. For example, the number of random spot scans orrepaint applications may be increased or decreased by specificallymapping raster scans to phases.

In one or more embodiments, the beam applications may be gated aroundthe periodic motion so that proton beam is not applied during or neartransition periods or when the target area accelerates, or otherwisemaximizes the application of the beam during periods of rest or constantmotion. Gating around the periodic motion may be accomplished by addingartificial delays or pauses in the timing sequence of the radiation planto delay application of the beam during transitions between phases, oreven to pause applications during specific phases.

At step 707, the proton (e.g., spot-scanning) beam is applied accordingto the adjusted radiation plan determined at step 705. In one or moreembodiments, the beam may be applied as a sequence of random spot scansfor one or more layers in a target area. In one embodiment, the scanningdirection of the beam application is aligned at step 705 to complementthe direction of the motion of the target area. For example, a targetarea may extend laterally during exhalation and retract duringinhalation. If an application requires more time than available (forexample by a duty cycle at using beam gating), a deliberate pause may beadded to the scan (e.g., a duration of a complete cycle of the periodicmotion). Thus, irradiations with scanned particles can be resumed whenthe target area is at the same position in space when the scan waspaused before.

In one or more embodiments, steps 703 through 707 may be performed inreal-time, such that the adjustment of a radiation plan and theapplication of a proton therapy beam may be aligned dynamically with thedetected motion of a target area.

According to some embodiments, the effectiveness of motion management isfurther improved using gating techniques.

According to some embodiments, potential effects of target are motionare mitigated using techniques such as rescanning by energy slice,rescanning of volume, repainting using random modulations, random delaysbetween repaints, scaled rescanning, isolayered rescanning, beamtracking, etc.

According to some embodiments, the target is irradiated using randomspot-scanning, where the spot size is variable and/or random. Thetreatment planning may consider motion interplay effects and use thevariable and/or random spot size to achieve homogenous dose distributionwhile mitigating or curing the motion interplay.

Exemplary Computer System

In one or more embodiments, alignment of the beam application with themotion of the target area may be executed as a series of programmedinstructions executed on a computing environment operable to control themotion and emission of the radiation therapy machine described abovewith respect to FIG. 1. FIG. 8 depicts such a computing environment,including computing system 800 upon which embodiments of the presentinvention may be implemented includes a general purpose computing systemenvironment. In its most basic configuration, computing system 800typically includes at least one processing unit 801 and memory, and anaddress/data bus 809 (or other interface) for communicating information.Depending on the exact configuration and type of computing systemenvironment, memory may be volatile (such as RAM 802), non-volatile(such as ROM 803, flash memory, etc.) or some combination of the two.

The computer system 800 may also comprise an optional graphics subsystem805 for presenting information to the radiologist or other user, e.g.,by displaying information on an attached display device 810, connectedby a video cable 811. According to embodiments of the present claimedinvention, the graphics subsystem 805 may be coupled directly to thedisplay device 810 through the video cable 811. A graphical userinterface of an application for grouping multiple beam fields may begenerated in the graphics subsystem 805, for example, and displayed tothe user in the display device 810. In alternate embodiments, displaydevice 810 may be integrated into the computing system (e.g., a laptopor netbook display panel) and will not require a video cable 811.

Additionally, computing system 800 may also have additionalfeatures/functionality. For example, computing system 800 may alsoinclude additional storage (removable and/or non-removable) including,but not limited to, magnetic or optical disks or tape. Computer storagemedia includes volatile and nonvolatile, removable and non-removablemedia implemented in any method or technology for storage of informationsuch as computer readable instructions, data structures, program modulesor other data. RAM 802, ROM 803, and external data storage device (notshown) are all examples of computer storage media.

Computer system 800 also comprises an optional alphanumeric input device806, an optional cursor control or directing device 807, and one or moresignal communication interfaces (input/output devices, e.g., a networkinterface card) 808. Optional alphanumeric input device 806 cancommunicate information and command selections to central processor 801.Optional cursor control or directing device 807 is coupled to bus 809for communicating user input information and command selections tocentral processor 801.

Signal communication interface (input/output device) 808, also coupledto bus 809, can be a serial port. Communication interface 808 may alsoinclude wireless communication mechanisms. Using communication interface808, computer system 800 can be communicatively coupled to othercomputer systems over a communication network such as the Internet or anintranet (e.g., a local area network).

In one or more embodiments, computing system 800 may be located in thesame treatment room or suite as the radiation therapy device 100described above with respect to FIG. 1. Alternately, computing system800 may also be located externally with respect to the treatment room orsuite containing treatment device 800.

By utilizing the systems and methods described above, the application ofirradiated particles (such as protons) can be directed with greaterprecision by aligning beam applications with the periodic motion of atarget area through the dynamic adjustment of beam characteristics andparameters. This alignment—all of which can be performed within asingle, computing system—can effectively reduce misdirected,under-radiated, or misapplied beam applications and provide a moreoptimized treatment or radiation plan for radiation subjects.

Although the subject matter has been described in language specific tostructural features and/or processor logical acts, it is to beunderstood that the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A method for irradiating a target area using randomly distributedspot locations, the method comprising: accessing a target radiationplan, the target radiation plan comprising a temporal and spatialsequence for administering a target dosage to a target area using afirst plurality of applications of a directed beam of protons;monitoring a movement of the target area; adjusting the target radiationplan to align the first plurality of applications of the directed beamof protons with the movement of the target area to generate an adjustedtarget radiation plan; painting the target area with the first pluralityof applications of directed beam of protons according to the adjustedtarget radiation plan; and subsequent to said painting, repainting afirst pattern of spot locations of the target area with a secondplurality of applications of the directed beam of protons, wherein thefirst pattern of spot locations is selected at random.
 2. The methodaccording to claim 1, further comprising, subsequent to said repaintingthe first pattern of spot locations, repainting a second pattern of spotlocations of the target area with a third plurality of applications ofthe directed beam of protons, wherein the second pattern of spotlocations is selected at random.
 3. The method according to claim 2,further comprising, subsequent to said repainting the second pattern ofspot locations, repainting a third pattern of spot locations of thetarget area with a fourth plurality of applications of the directed beamof protons, wherein the third pattern of spot locations is selected atrandom.
 4. The method of claim 2, wherein said repainting the secondpattern of spot locations results in a relatively uniform dosedistribution applied to the target area.
 5. The method according toclaim 2, wherein the proton beam comprises a spot scanning proton beam,a first spot scanning sequence is selected at random for the firstpattern of spot locations, a second spot scanning sequence is selectedat random for the second pattern of spot locations, said repainting thefirst pattern of spot locations is performed using the first spotscanning sequence, and said repainting the second pattern of spotlocations is performed using the second spot scanning sequence.
 6. Themethod according to claim 5, wherein said repainting the first patternof spot locations comprises applying a first fraction of the targetdosage to each of the spot locations in the first pattern, saidrepainting the second pattern of spot locations comprises applying asecond fraction of the target dosage to each of the spot locations inthe second pattern, and a cumulative dosage from applying the first andsecond fractions of the target dosage to the first and second patternsof spot locations is substantially equivalent to the target dosage. 7.The method according to claim 2, wherein a first spot scanning sequenceis selected for the first pattern of spot locations, a second spotscanning sequence is selected for the second pattern of spot locations,said repainting the first pattern of spot locations is performed usingthe first spot scanning sequence, and said repainting second pattern ofspot locations is performed using the second spot scanning sequence,wherein the first and second spot scanning sequences are selected tooptimize at least one of a scanning efficiency, a dose homogeneity, anda balance between the scanning efficiency and the dose homogeneity. 8.The method according to claim 1, wherein the movement of the target areacomprises a plurality of phases of periodic movement delineated by aplurality of transition periods between the plurality of phases ofperiodic movement.
 9. The method according to claim 8, wherein saidadjusting the target radiation plan comprises at least one of: aligninga starting position of an application of the directed beam of protonswith a direction of a phase of periodic movement; adjusting a number ofrandom repainting scans for producing the target dose; adjusting anumber of randomly selected spot locations for producing the targetdose; adjusting a dose rate of an application of the directed beam ofprotons based on a phase of periodic movement; and gating applicationsof the directed beam of protons outside of the plurality of phases ofperiodic movement wherein the directed beam of protons is not applied tothe target area during a transition period.
 10. The method according toclaim 1, wherein said adjusting the target radiation plan comprisesinserting a plurality of pauses in the timed sequence of the targetradiation plan to align the first plurality of applications of thedirected beam of protons with a frequency of the movement of the targetarea.
 11. The method according to claim 1, wherein the movement of thetarget area comprises a movement corresponding to at least one of: arespiratory cycle; and a cardiac cycle.
 12. The method according toclaim 1, wherein the target area comprises an organ.
 13. A radiationapplication system comprising: a particle accelerator configured toproduce a plurality of irradiated particles; a gantry configured toreceive the plurality of irradiated particles and to rotate around atarget subject; a treatment nozzle comprised in the gantry, thetreatment nozzle configured to emit the plurality of irradiatedparticles as a directed beam at a target area in the target subject; anda computing device coupled to the gantry and comprising: a memory deviceconfigured to store a target radiation plan comprising a timed sequencefor administering a target dosage to the target area by irradiating thetarget area with a first plurality of applications of the directed beamof the irradiated particles; and a processor configured to adjust thetarget radiation plan to align the plurality of applications of thedirected beam of the irradiated particles with a movement of the targetarea, and to program a movement of the gantry around the target subjectand an emission of the treatment nozzle to irradiate a pattern of spotlocations in the target area with a second plurality of applications ofthe directed beam of irradiated particles, wherein the pattern of spotlocations is selected at random.
 14. The system according to claim 13,wherein the directed beam of irradiated particles comprises a spotscanning proton beam.
 15. The system according to claim 14, wherein thedirected beam of protons applies a fraction of the target dosage to eachof the spot locations, wherein a collective dosage from applying thefractions of the target dosage to the spot locations is substantiallyequivalent to the target dosage.
 16. The system according to claim 15,wherein the movement of the target area comprises a plurality ofrepeating movement phases corresponding to at least one of: arespiratory cycle; and a cardiac cycle.
 17. The system according toclaim 16, wherein the processor is further configured to adjust thetarget radiation plan by performing at least one of: an alignment of astarting position of an application of the directed beam of irradiatedparticles with a direction of a phase of periodic movement; anadjustment of a number of random repainting scans for producing thetarget dose; an adjustment of a number of randomly selected spotlocations for producing the target dose; an adjustment of a dose rate ofan application of the directed beam of irradiated particles based on aphase of periodic movement; and a gating of applications of the directedbeam of irradiated particles outside of the plurality of phases ofperiodic movement wherein the directed beam of irradiated particles isnot applied to the target area during a transition period.
 18. Anon-transitory computer readable medium comprising a plurality ofprogrammed instructions which, when executed by a processor in acomputing system, is operable to implement a target radiation plan usingrandomly distributed spot locations, the computer readable mediumcomprising: instructions to access a target radiation plan, the targetradiation plan comprising a timed sequence for administering a targetdosage to a target area using a first plurality of applications of aspot-scanning beam of protons; instructions to monitor a periodicmovement of the target area; instructions to generate an adjusted targetradiation plan by adjusting the target radiation plan to align the firstplurality of applications of the directed beam of protons with movementof the target area; instructions to scan the target area with the firstplurality of applications of directed beam of protons according to theadjusted target radiation plan; instructions to rescan, after the firstplurality of applications, a first pattern of spot locations of thetarget area with a second plurality of applications of the directed beamof protons, wherein the first pattern of spot locations is selected atrandom; and instructions to rescan, after the second plurality ofapplications, a second pattern of spot locations of the target area witha third plurality of applications of the directed beam of protons,wherein the second pattern of spot locations is selected at random. 19.The computer readable medium according to claim 18, wherein theinstructions to adjust the target radiation plan comprises at least oneof: an alignment of a starting position of an application of thedirected beam of irradiated particles with a direction of a phase ofperiodic movement; an adjustment of a number of random repainting scansfor producing the target dose; an adjustment of a number of randomlyselected spot locations for producing the target dose; an adjustment ofa dose rate of an application of the directed beam of irradiatedparticles based on a phase of periodic movement; and a gating ofapplications of the directed beam of irradiated particles outside of theplurality of phases of periodic movement wherein the directed beam ofirradiated particles is not applied to the target area during atransition period.
 20. The computer readable medium according to claim18, wherein the target area comprises an organ.